Students who demonstrate understanding can: Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism.
Clarification statement: Emphasis is on describing that molecules are broken apart and put back together and that in this process, energy is released.
Assessment boundary: Assessment does not include details of the chemical reactions for photosynthesis or respiration.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
A sandwich does not stay a sandwich once you eat it. Digestion breaks large food molecules, such as starch, proteins and fats, into smaller pieces. Those smaller molecules travel through the body and are put back together in new ways. Some are rebuilt into the proteins and other molecules that make new muscle, skin and blood cells. Others are broken down further inside cells, combining with oxygen in cellular respiration to release energy that powers movement and keeps the body warm.
Students develop a model that shows this rearrangement. Atoms are not created or destroyed; they are regrouped. That is why the mass of food eaten must end up somewhere: in new body tissue, in carbon dioxide and water breathed out, or in wastes. The same logic applies to plants, which rearrange the sugar they make into cellulose, starch and other molecules.
The emphasis is on the idea that molecules are broken apart and put back together, and that energy is released in the process. Detailed chemical reactions are not required.
Matter does not become energy in the body. Food molecules are rearranged, and the energy stored in their bonds is released when they react with oxygen.
Most of the mass from food used for energy leaves the body as carbon dioxide and water vapor that we breathe out.
Digestion breaks food into small molecules in the gut. Cellular respiration releases energy from those molecules inside cells. They are linked but separate processes.
Use a model to explain what happens to the protein and fat in a peanut after a student eats it.
Answer: The peanut's molecules are broken apart and reassembled: some atoms become part of new body tissue, others are used in respiration to release energy and leave the body as carbon dioxide and water.
Physical models work well: snap-together beads or building bricks let students break apart a 'food molecule' and rebuild the same pieces into a different 'body molecule', making it obvious that no pieces are lost or created. Ask them to account for every brick at the end.
Link back to photosynthesis by having students trace one carbon atom from the air, into a plant sugar, into a person, and back out as carbon dioxide. Avoid detailed equations, which the standard leaves out.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: D) They are broken into smaller molecules
Digestion breaks large molecules into smaller ones that can be absorbed and used.
Answer: A) Oxygen
Cellular respiration uses oxygen to release energy from sugar and other food molecules.
Answer: cellular respiration (also accepted: respiration)
Cellular respiration releases energy from food molecules, producing carbon dioxide and water.
Answer: C) Food the child has eaten
Atoms from food molecules are rearranged into new body molecules for growth.
Answer: D) It is breathed out as carbon dioxide and water
Fat is broken down in respiration, and its atoms leave mostly as carbon dioxide breathed out, plus water.
Answer: no
Atoms are rearranged, not created or destroyed.
Support an argument that plants get the materials they need for growth chiefly from air and water.
Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed, resulting in a net transfer of energy.
A full lesson with slides, activities and an exit ticket on food, new molecules and energy release, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-LS1-7 with an answer key, ready in about a minute.
Make a worksheet βTurn food, new molecules and energy release into a quiz students answer online that marks itself, with a class summary for you.
Build a test βNo. The assessment boundary excludes details of the chemical reactions for photosynthesis and respiration; students model molecules being broken apart and rebuilt.
MS-LS1-6 focuses on how photosynthesis brings matter and energy into organisms. MS-LS1-7 follows what happens to food molecules after they are inside an organism.