Answer:
B) Heat is given off.
Explanation:
When heat is given off, a chemical change must have occurred and such a reaction is termed an exothermic reaction.
A chemical change is one in which;
- the process is not easily reversible
- leads to the production of new kinds of matter
- involves change in mass
- requires a considerable amount of energy.
Most chemical reactions are accompanied by heat changes.
The correct answer is A. Chemical change turns food into a new form, a form that cells can use. It happens because the food we eat cannot be processed by cells so several reactions inside our body allow chemical changes to the food we ate turning them to usable compounds for our cells.
1. Metallic bond is a type of chemical bond.
2. Metallic bond is formed between electrons and positively charged metal ions.
3. Metallic radius is defined as one-half of the distance between the two adjacent metal ions.
4. Metallic bond increace electrical and thermal conductivity.
5. Metals conduct heat, because when free moving electrons gain energy (heat) they vibrate more quickly and can move around.
Answer:
Option A is correct. Statements b,c and d are true
Explanation:
Step 1: Data given
Proton = a subatomic particle with a positive electric charge of +1 and a mass slightly less than that of a neutron.
Neutron = a subatomic particle of about the same mass as a proton but without an electric charge
electron = a subatomic particle whose electric charge is negative one elementary charge.
The mass of an electron is only about 1/2000 the mass of a proton or neutron, so electrons contribute virtually nothing to the total mass of an atom
Step 2: Statements
(a) Protons have a charge of -1.
This is false. Protons have a charge of +1
(b) Neutrons have no charge.
This is true
(c) An electron has negligible mass compared to the mass of a neutron
This is true
(d)Number of proton equals to number of electrons on a stable atom
This is true. A stable atom has a charge of 0. this means the same amount of protons and electrons
Option A is correct. Statements b,c and d are true
